Cadmium plating



Aldaoets *Amoreaction Product Amaldacets4 N- Containing Ox idzed Amoreaction Product R. o. HULL CADMIUM PLATING Filed Oct. 17, 1955 Midway@ s Acetaldehyde Aldol l Crotonaldehyde l l l l l l l r "1 r- L-'Tn'i ^m Alkaline ""'f-m Lsolufion l l l J Amoa+ b reaction reaction Product Product -1 r- Oxidation Oxidation l L l I i N-Co tainn N-Containing oxidized I g indi-Zed Cyanidepmg'reocno reaction ro uc Product f INVENTOR.

RICHARD O. HULL.

ATTORNEY.

Patented Aug. 17, 1937 UNITED ASTATES .PATENT OFFICE CADMIUM PLATING Richard 0. Hull, Lakewood, Ohio, assignor, by mesne assignments, to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation oi*` Delaware Application october 17, i935', serial 45,402

17 claims.. (C1. 204-1) This invention relates to the electrodeposition of cadmium from cyanidecadmium baths, and is particularly directed. to cyanide-cadmium plating compositions, plating baths, and plating processes which employ, as an addition agent, an oxidized amketaldoresin whereby a bright, smooth, uniform cadmium deposit is obtained.

It has heretofore been proposed to modify the character of cadmium deposits by the use of organic addition agents such as sulte cellulose waste, dextrin, starch, alkylated naphthalene sulfonic acids, wool, caieine, shellac, casein, licorice, glucose, alkali reaction productspf heterocyclic aldehydes, furfural, gum arabic, and

l5 gelatine.

It has been necessary to employ an addition agent and/or a brightener with cyanide-cadmium plating baths, because, without such modifying agents, cadmium deposits of exceedingly poor character and appearance are obtained. The properties of electrodeposited cadmium are largely determined by the addition agent and/or brightener used, and the desirability of a cadmium plate is, to a, great extent, dependent upon the eicacy of themodifying agents employed.

The properties of a cadmium plate are partly dependent, in commercial practice, upon certain characteristics of the plating bath employed, and these characteristics can be modified, to some 3 extent, by suitable organic addition agents and/ or brighteners. Under strictly controlled conditions, one can deposit a fairly satisfactory cadmium'plate on a at cathode with a bath which, in ordinary commercial practice, -would be un- 5 satisfactory. Under the usual conditions of -commercial operation, particularly when recessed articles or articles of irregular shape are to be plated, a bath must have a fairly wide bright current density range and good throwing power 40 if even moderately satisfactory results are to be obtained. The throwing power and the extent of the bright range have been somewhat improved bythe use tofore known.

While the addition agents hitherto employed have eieoted a considerable improvement in processes for the electrodeposition of cadmium,

the results obtained have not been all that ,could l be desired.

I have found that the oxidation products of certain derivatives of ketaldones are exceedingly effective addition agents for cyanide-cadmium plating. By the use of these novel addition agents, itis possible to electrodeposit cafdmium` from cyanide-cadmium baths as a bright, smooth,

of the addition-agents hererials from which my addition `agents are de-v rived. The starting materials are designated ketaldones but, as will be explained below, certain ketaldones are particularly suitable for my f purpose.

My preferred starting materials are, generally speaking, aliphatic and carbocyciic ketaldones, that'is aldehydes and ketones, but, as will become apparent hereinafter, the best results are obtained by the use of certain .aliphatic and carbocyclic aldehydes and ketones.

'Ihe term ketaldonyl has been applied to designate the C=O group as it appears in aldehydes and ketones in contradistinction to the C=O group as it' appears in acids. Of course, the carbonyl group as it appears .in acids,

is very diierent in its properties from the carbonyl group as it appears in aldehydes and` ketones, and the expression ketaldonyl group is employed to distinguish the aldehydic and the .ketonic carbonyl group from the acidic carbonyl.

group. The expression ketaldonyl group as used herein designates a carbonyl group in Vwhich a third carbon valence is joined to carbon and in which the remaining valence'is satisfied by carbon or by hydrogen. Or, in chemical symbols, the ketaldonyl group as used herein is of the type wherein R isa hydrocarbon radical and wherein Rf is hydrogen, in the case of an aldehyde, or R' is a hydrocarbon radical, in the case of a ketone. It will also be understood that the ketones and aldehydes themselves 'are referred to herein as ketaldones in accordance with this terminology. The starting materials which I employ are..

I broadly, ketaldones. While I may use aldoses, 5 ketoses, lheterocyclic aldehydes and ketones and any other such ketaldones, I prefer to use `aliphatic and carbocyclic ketaldones which do not contain a carboxyl group, which do not contain sulfur,and which do'not contain'nitrogen. The e starting materials, moreover, should contain no more than two hydroxyl groups and preferably should contain at least two carbon atoms. More specifically, I prefer to employ ketaldones which contain only carbon, hydrogen, and oxygen, which l5 contain at least two carbon atoms, and in which As is illustrated in the drawing, thestarting..

materials, the ketaldones, are reacted with ammonia or -an amine, in alkaline solution, to produce an amo-reaction product. It willbe observed that amo is used to designate both ammonia and an amine. As will be noted hereinafter, theamo-reaction products of the ketal- J.25 dones are very similar in their physical an chemf ical characteristics. They all contain trogen, and all are, apparently, Y complex mixtures. I

have accordingly, designated these reaction products amketaldoresins. The nature of the .30 products and the nature. of the reaction will be discussed in more detail hereinafter.

The amketaldoresins are subsequently modified by oxidation toyield nitrogen-containing derivatives which are effective as addition agents.

1 35 These derivatives, while more effective, are very similar to the'amketaldoresins, ordinarily differing slightly as to color and solubility. Y

A preferred group of ketaldones, the aldacets, are illustrated in the upper right-hand corner' of v .40the drawing. More will be said Ihereinafter re garding the members of the illustrated aldacet f equilibrium. As is shown in the drawing, the aldacets, like the ketaldones generally, are reacted with animonia, an amine, or cyanide to 45 produce an amketaldoresin., The particular amketaldoresin produced from the aldacets are designated herein, the amaldacetsk According to my invention the amaldacets are oxidized, as were the amketaldoresins generally, to produce nitrogen-containing derivatives.`

The ketaldones which I employl as starting materials are reacted in weak alkaline solution with an amo to produce an amo-reaction product from which addition agents of my invention may be prepared. As will be noted hereinafter, the use 4.

' A-rate of conversion apparently depending upon the specific aldacet. first present. The aldacet equilibrium is'illustrated in the upper, right corner of thevdrawing. Q

75 Referring to' the aldacet equilibrium in more 'the hydrogen-oxygen ratio is greater than that,

detail, it is noted that acetaldehyde in dilute'alkaline solution is quickly converted to aldol thus:

`The aldol may lose one molecule of Water and become crotonaldehyde, thus:

The aldol may condense to form paraldol, thus:

In order to visualize the relationships existin between-the aldacets, reference should be had l to the accompanying drawing wherein these relationships are diagrammatically illustrated. It

vis to be understood that the relationships are shown with reference to the compounds in dilute alkaline solutions or in alkali metal cyanide solutions. v

In the drawing, acetaldehydefis illustrated as converting to aldol. ^The aldol maygo to paraldol or to crotonaldehyde. The aldol might go back to acetaldehyde, but only to a small extent. The paraldol may go. back to aldol, or itmay lose l water and go to crotonaldehyde, though this latter conversion probably takes place t'o a very small degree. The crotonaldehyde may form from acetaldehyde, aldol, or paraldol, and, by gaining water, may revert to any of them, though it is likely that it would nove largely by way of aldol. v l

As is seen in the drawing, then, I may consider the aldacets as being in equilibrium. 'I'his equilibrium will, according to my belief, be substantially the same regardless of' which of the four substances are initially added to the cyanide solution, though, as will hereinafter be noted, the aldacets are not entirely equivalent, and it is possible that some of the aldacets in dilute a1- kaline-solution form this aldacet equilibrium` rather'slowly or move more rapidly in certain directions than in others.

While I have-mentioned-only acetaldehyde, aldol, crotonaldehyde, and paraldol as members of this sub-genus, I may use anycondensation product of acetaldehyde in dilute alkali solution. Anotherv aldacet is paraldehyde. Ordinarily paraldehyde is considered as `forming only in acid solution, but I have` reason tol believe that at least some paraldehyde forms in the discussed aldacet equilibrium. Paraldehyde is apparently very slow to convert to other aldacets and probably because of this fact is none too satisfactory a starting material.

Aldol, acetaldehyde, crotonaldehyde, and paraldol are the only commercially available aldacets at the present time. For practical reasons, therefore, 1 prefer to usev as a starting material an aldehyde selected from the group consisting of acetaldehyde, aldol, 'crotonaldehyde,' andv paraldol.

It is to be noted that the aldacets are those aliphatic ketaldones, such as acetaldehyde, aldol, crotonaldehyde, and paraldol, which exist in some sort of equilibrium when one of the said ketaldonesl is -put into alkaline or valkali metal cyanide solution. Generally then, one might-say -that the aldacets are aliphatic aldehydes lfrom This may be attributable to the fact that crotonaldehyde is but slowly converted to the necessary form, or to some other now unknowncause.

As is above indicated, there is considerable uncertainty as to'the extent and nature of the con` version of some aldacets to others. All of the evidence now available to me substantiates the putative theory advanced above as to the nature of the aldacet equilibrium, but it will be understood that direct experimental evidence is obtainable only with great difficulty. In most instances the aldacet equilibrium exists for only \,a short time, some further action quicklyl taking place to form resins. That the aldacets are in some kind of equilibrium is relatively certain, but the proportions of individual aldacets and the rates of conversion have, to date, deed exact determination.

It is clearly to be understood that the above description of the relations` between the initial materials is lfor purposes of` illustration and that I do not intend to be limited in any way thereby, because the chemistry of these compounds is intricate and obscure, and because my results are obtained entirely apart from theoretical considerations. It is also to be understood that while I refer to aldol, acetaldehyde, crotonaldehyde, and paraldol as resulting from the condensation of acetaldehyde in alkaline solutions, I do not wish to be limited thereby, as I may use aldol, acetaldehyde, crotonaldehyde, and paraldol which have been made in any manner.

Turning now to a consideration of the amketaldoresins produced from the aldacets, it is rst noted that the specific amketaldoresins produced by the reaction of the aldacets with amoes or cyanide in alkaline solutions are termed amaldacets. The amaldacets are almost indistinguishable from one another in physical and chemical properties though,' as will be noted hereinafter, they differ slightly from one another as to their eiilciency as addition agents for cyanidecadmium plating.

It is to be noted that the 4term reaction i s` used to express whatever occurs when the ketaldones, or specifically the aldacets, are 4treated 'in alkaline solution with cyanide -or with an amo. The term "reaction is used to distinguish from condensation as used above with reference to the aldacet equilibrium tho, in fact, the

reaction probably includes both polymerizations and condensations.

each twoI molecules of The amaldacets as well as the arnketaldoresins contain nitrogen as determined by the Kjeldahl method; In the amaldacets the nitrogen is present in about the ratio of one nitrogen atom to ldol- (four of acetaldehyde, one of paraldol, ete). I have been unable to determine how the nitrogen is located in the amaldacet molecules, and insufficient evidence is available to warrant any assumptions.

aldacets. This reaction That the amaldacets are not simple compounds, but are complex mixtures, is evidenced by the fact that portions are water-soluble, other portiors chloroform-soluble, etc. It seems probable that the amaldacets are the result of many intricate polymerizations, condensatlons, and reactions. There maybe some condensation products which' are not combined with nitrogen, but the fact that a molecular proportion, or an excess, of an amo or of an alkali metal cyanide, to aldehyde give the best results, leads to the belief that the amount of such uncombined products is relatively small.

The reaction which leads to the amaldacets takes place, I believe, between ammonia, an amine, or possibly CN- and one or more of the is illustrated in the drawing by dashed lines. The aldacet, or aldacets, which react with the nitrogen compound may go firstto some other and unknown form and then react. I conceive of the reaction as withdrawing one, or more, of the aldacets from the equilibrium with the result that the remaining aldacets move towards the removed materials to restore the equilibrium,` and are so all nally utilized.

I have reason to believe that two or more of the materials in equilibrium react with 4cyanide to produce the nal product, or else the one which reacts with the cyanide moves thru a number of different paths to produce a number of nal products. This is evidenced by the fact that the reaction product is a mixture of separable materials. More is said of this separability hereinafter.

To illustrate the production-of the amaldacets by the reaction of aldacets. with ammonia or amines, the following specific examples are given:

Example I Equimolecular proportions of crotonaldehyde and monoethanolamine were reacted, starting the reaction at room temperatures. The temperature of the mixture was held at about forty to fifty degrees centigrade until no further reaction was apparent. The reaction mixture was a reddish-brown, viscous liquid, readily soluble in cyanide-cadmium plating baths.

Example II A similar amaldacet was produced by reacting equimolecular proportions of aldol and monoethanolamine. A product exceedingly similar to the one of Example I was produced.

Example III Example IV Equimolecular proportions of aldol and diethanolamine were reacted at room temperatures. A product very similar to those of the above examples was produced, the product of this-example, however, being slightly less soluble than the t product of Examples I and II.

. Example V 4 'what less soluble than the products of Examples I and 1I.

. Example VI 5 Aldol was treated with ammonia gas by bubr bling the gas through the aldol until no further reaction was noted: The reaction product, when oxidized, was rather diicultly soluble, and`was only a moderately eilicient. addition agent for cyamide-cadmium plating baths.

Example VII Eq'luirnolecular` proportions of crotonaldehyde and ammonium hydroxide were reacted. 'I'he reaction product was very similar to that of the preceding example. After several days, the amaldacet of this example solidiiled, bemi'ng much less soluble.

Example VIII l Crotonaldehyde and ammonia gas were reacted at about twenty-five degrees centigrade. The product was very similar to that 'of the preceding example. After a'few days the product of this example solidied to abrittle, red r`esin.

'ExampleIX Acetaldehyde was treatedwith an excess of 30 gaseous ammonia. An amaldacet similar to that of the preceding example was obtained.

While I have shown the reaction of the aldacets with ammonia, ammonium hydroxide, and with `certain amines in 'the above examples, it will be 35 understoodtnat-other amoes may be used. I

' may, for instance, prepare the amaldacets byA treating the aldacets with amines such as the glucamines, for instance, glucamine and methyl glucamine, or aliphatic amines, for instance, 40 methyl ethylamine, methylamine, and `ethylamine.

'While the amaldacets may be prepared by con- `ducting the reactions of the above examples at rather widely varied temperatures, I prefer that 4-4l'5 the reaction be-performed 'at temperatures" be- '55 It is generally preferred to employ an equimolecular proportion, or an excess,'of amine to aldehyde. As will be. noted by comparing Examples II and III, less satisfactory'amaldacetsfare produced when less thanan equivalent ani'gunt of amine is used.

Instead of preparing the amaldacets by the direct reaction of ammonia or amines with the aldacets, they may be prepared' by reacting the aldacets with aikan cyamdesl When the`aldacets are treated with liquid hy-v drocyanic acid, some slight reaction apparently occurs, but the product has but little; lif any, ac- ,tivityjas an addition agent in cyanide-cadmium plating baths, and oxidation according to my in- `vention elfects little improvement.' From this fact it appears that when the aldacets rea'ctedwith alkali metal cyanides, no greatprtion of the reaction product contains the CN- group. The cyanides lare known to hydrolize to produce ammonia and formates according "-to the following illustrative reaction:

It seems possible, accordingly, that the cyanide '5 is hydrolized, and lthat the aldacets react with the ammonia which'is formed, 'This hypothesis is supportedby'the fact 'that the odor of ammonia is apparent throughout the reaction.

This hypothesis is further supported bythe l1 fact that the reaction products of the aldacets with amoes and with cyanide are very similar. vWhile verysimilar, -the reaction products of aldacets with alkali metal cyanides are somewhat more desirable than the reaction products L of the aldacets with amoes.

If, as I have assumed, the reaction with cyanide amounts to a reaction with ammonia by reason of the hydrolysis oi the cyanide, it is surprising that such a difference in theamaldacets 21 should exist. It seems possible, however, that the'di-fferences are attributable to the fact that in an alkali metal cyanide solution the ammonia is somewhat less available.K It is possible; ofcourse, that some of the-aldacet reacts with 21 the cyanide directly or with some intermediate product ofl'the hydrolysis. It seems probable, however, thatthe reaction occurs largely be- 'tween the al'dacet and, the ammonia produced by hydrolysis of the'alkaline cyanide solution.

The-following specific examples illustrate the production of the amaldacets by the reaction of aldacets with an alkali metal cyanide.

. Example X x a,

. peraturel was maintained for about two and onehalf hours, cooling or heating the. receptacle as required. A s the aldol was added, and for .a

time thereafter, the heat of the reaction necessitated a continuous coolingof` the reaction mix- 5( ture to h'old the temperature within the desired limits. Later it became necessary to supply heat to the reaction mixture to maintain theA temperature. During the reaction a small amount of ammonia was liberated, as was evidenced bythe 5g characteristic odor.

The amaldacetfcontaining reaction mixture.

obtained may immediately -be oxidized toform.

one product of my invention. It is a thick, mo-

bile liquid, dark red in color. 6(

vIn order -to purify and concentrate this reaction product, the solution, after being allowed. to cool, was made neutral to litmuswith a dilute solution of sulfuric acid. The acid solution consisted of one 'part lby volume of'water to 65 one part byl volume of concentrated sulfuric acid. Thefrewasthen added an excess of ten per cent over the volume of dilute acid required tol neutralize the Sodium sulfate was precipitated, and theexcess acid used depressed its 7( solubility.v The temperature.was-n ot allowed to go above 50 C. during this neutralization treatment. Hydrocyanic acid gas' was evolved during4 the treatment and means were provided for dispotins gilit. u

l The acid treated solution was allowed to stand for severalhours and a dark red fraction rose to the top. This top layer was removed andv centrifuged. The separated top layer, which may be oxidized, to fom a preferredproduct of my in-v vention, i-s a viscous liquid, dark red in color, and it has a specic gravity of about 1.20. At temperatures as low as 17 C. it remains liquid,

but at the temperature produced witha freezing jzene, and.- petroleum ether. It is, however, completely soluble in alcohol and acetone.

The products of this example are entirely soluble in cyanide plating baths up'to about three grams per liter. One characteristic of both the final product and the unseparated reaction mix.

ture is that when used in cyanide cadmium plating baths they exhibit the property of causing a bright deposit of cadmium. This characteristic serves admirably for the identification of these novel products.

The amaldacets of this example are not chemical compounds, but are mixtures as is evidenced by the fact that portions of the products are water-soluble and a smaller portion of the prod- 30 ucts is chloroform-soluble. When used as an addition agent in electroplating cadmium, the water soluble portion exhibits the property of promoting the-formation of a bright finish o-n recessed parts' of an article. The water insolu- 35 ble portion seems to exercise its major influence on the brightness of the less recessed parts of the article. The chloroform soluble fraction is very active as an addition agent, but when used alone it is not satisfactory as it causes streaks and 40 stains on the plated article.-

The temperature of the reaction is relatively important as the yield of the product and its activity as an addition agent seem to be greatly influenced thereby. The activity and. of course,

45 the yield of the oxidation products of this invention are similarly influenced. The best results seem to be obtained with temperatures between about 45 and 50 C. as used in this example. If lower temperatures are used, there is a decrease 50 in the vactivity of the product as anr addition agent. Below about 30 C. the product rapidly becomes less active with decreases in temperature. If temperatures substantially above 50 55' are used, the yield of active material is smaller. At about 75 C., for instance, about one-half of the product is an insoluble resin without much value as an addition agent. Generally, I may use temperatures from about 30 C. to about 75 C., tho more specifically I prefer to keep the reaction temperature between about 45 and 50 C. so that oxidation products of optimum` characteristics may be produced from these materials.

The separation by neutralization with acid was 65 accomplished at 50 C., but rigid temperature control is not necessary. Apparently, as soon as the reaction is complete, the reaction product maybe heated to rather high temperatures with- 'out substantial damage resulting,

7o In the examples, sulfuric acid'is employed for removing, excess sodium cyanide by converting sodium cyanide will readily occur to those working in the art. y

While I may use any of the aldacets as a starting material, I prefer to use aldl because it is readily obtainable commercially at the present time andbecause it leads to somewhat higher yields than do some of the other aldacets, crotonaldehyde and paraldehyde for instance. Alsol is also advantageously employed by reason of its being less volatilethan acetaldehyde and more easily handled than paraldol which is a solid.

As an example of the y'preparation of an amal- Vdacet from another aldacet, I give the following:

Example XI I Eighty'pa'rts by weight of acetaldehyde was added slowly to 100 parts by weight of water con-f taining 20 parts by weight of sodium cyanide. The temperature was held between 40 and 50 C. for. about one-half hour, at the end of which time the product was allowed to cool.

The resulting amaldacet solution may be oxidized to produce one product of my invention.

The reaction mixture is preferably concentrated by treatment with dilute sulfuric acid, as described in Example X. The product is 4substantially identical with the .concentrated product of Example X described in detail above.

It is noted that in Example XI a smaller ratio of cyanid'eto aldehyde was used than in Example X. This seems to lower the yield of active material somewhat. Generally, the best results are obtained when the aldehyde and cyanide are used in substantially molecular proportions, but a latitude is permissible.

. If less ofthe alkali metal cyanide be used, the product will be less active, while if an excess of alkali metal cyanide be used, no particular damage results. When the product is concentrated by neutralizing with dilute sulfuric acid, the excess of cyanide, over that required to form the reaction product, is converted to alkali sulfate yield is low. 4The time of Example Xl representsa practical minimum, and I usually prefer to employ a longer period. In general, the reaction temperature should be maintained for not less than about one-half hour, and I prefer to maintain it for not less than about four hours to obtain la product which, when oxidized, yields an addi-v tion agent of the highest activity.`

The following examples illustrate the production of products which have a lower ratio of hydrogen to oxygen than have the amketaldoresins, which products constitute addition agents of my invention:

Example XII The cyanide reaction product" of the above Example X was subjectedto oxidation by adding thereto ten cc. per liter of 100 volume (30% by weight) hydrogen peroxide. The product thusobtained was concentrated byV acidification with sulfuric acid according tothe procedure of the above Example X.

Employing the concentrated product as `an addition agent, cyanide-cadmium platingbaths were made upas follows y:

( 1) Grams per liter 5 sodium cyanide Naam A 13o` Y Cadmium oxide (CdO) f Sodium sulfate (Na2SO4) Cobalt sulfate (CoSO47HzO) e Addition agent A plating solution Was made up and used in the customary way to plate a number of articles with a cadmium deposit about lve-thousandths of an inch thick. After washing with water, the articles were examined and found to have a perfectly smooth, mirrorlike nish. It is, of course, very diilicult withprior art processes to obtain even a fairly smooth finish when so thick .a

3o (2) Gram per liter cadmiumbxide todo) Sodium cyanide (NaCN) l 120 r Addition agent 0.6

5 This bath was used for plating several objects Yat a current density of twenty amperes per square smooth. The number of grams of cadmium oxide in the above "bath may be varied between fifteen and forty and good results will be obtained. If the bath be too concentrated the deposit will not be entirely satisfactory.

The oxidized, dilute solution was used in a similar manner with similar results. About five grams per liter were used with bath (1) and about three grams per liter were used with bath (2).

It is noted that less of the concentrated product was used than f the reaction mixture. The amounts used in eachinstance, however, repre-1 sent the amount of product produced from substantially the same amounts/of'laldol.

The oxidized amaldacets are slightly more soluble and are more eiective as addition agents in cyanide-cadmium plating baths than the untreated amketaldoresins from which kthey are derived. u

. Example XIII The reaction product of Example XI was oxi- 0 dized, according to the procedure of the above Example XII, and theoxidized product concentrated. The oxidized reaction productand the concentratedproduct produced results comparable with those vobtained above with they addition agent of Example XII.

Example XI The crotonaldeliyde-monoethanolaniineA reaction product of Example I was oxidized with hydrogen peroxide. This oxidized product gave results comparable to those obtained according-to Example XII when employed in cyanide-cadmium baths such asv are there shown.

The other amaldacets shown above in Examples i1; 111,1v, V,V1,VII, VIII, and IX may similarly Thel deposit, was extremely brightl and b e oxidized to produce improved addition agents of my invention. u'

While hydrogen peroY de has been particularly mentionedv in the above examples as an oxidizing agent, it will be ev'iie'rltY toY those skilled in the art that other suitable 'oxidizing agents such as sodium or potassium permanganates may be em- -f' ployed. The extentof oxidation may be widely varied, but it will be evident that the oxidation must not be carried too far. Generally, any

amount of oxidation may 'be employed provided the lcarbon skeletons of the compounds 'are not broken up. shouId contain nitrogen.

Some of the oxidation products of the hereto fore mentioned amaldacets, such. asan oxidaftion' product of the amaldacet of Example VI,

are not readily solublein cyanide-cadmium plating fbaths, and it is desirable that they be lispersed inlthe baths. With the oxidation productsofithe amketaldoresins generally, likewise, it is expedient to disperse the addition agent if dim- ,culty is encountered in dissolving an'j optimum quantity. The addition agents maybe dispersed and their dissolution aided by adding them to a cyanide-cadmium bath in a-suitable solvent, suchl as alcohol or acetone. It may sometimes be The -oxidized product, of course,l

found desirable to reduce the addition agents to a iinely divided state, or to use 'them in conjunction with such dispersing agents as saponin, gum arabic, and sulte cellulose waste.

While 'my addition agents are effective in any customary cyanide bath, I prefer to use bathsof the kind set forth in U. S. Patent 1,681,509 to Mr. Leon R; Westbrook, and as shown in Ex- -f ample IUI, bath (l). These baths areuof the cyanide type, and contain -a small amount of a compound of a metal of the iron group hav'ing an atomic weight greaterv than fty-eight. The details as to the formulation and use of these baths may be found'- in the said Patent 1,681,509 and need not be duplicated here.

The plating ramsl urine said Patent 1,681,509

.A are modied, as shown above, only by employing my novel addition agents in lieu ofthe addition agents, goulac, \dextrin, starch, etc., mentioned therein. While the. plating processes` described in the said Patent 1,681,509 lead to a bright, hard,

. dense, and smooth deposit of cadmium, and while the invention therein described andclaimed has 'been widely .accepted by' the art because of its merit, the substitution of my addition agents for those in the patent results in a cadmium deposit` of even greater smoothness, uniformity, and

brightness.

Of course, I may use other compounds of metals of the iron group having an atomic weight greater than fifty-eight, such as nickel, copper, etc., as

disclosed in the heretofore mentioned Patent 1,681,509-, but tlie use of cobalt compounds as in Exlample XII, bath (1), has led to the best results. j I

I desire that it be clearly understood that the whole disclosure of the heretofore mentioned Patent 1,681,509, as'well as that of U.y S. Patent 1,564,413 to Clayton M. Hoi, cited therein, is to be considered, in-itsl entirety, as an integral part poi my disclosure, -as my novel addition agents co-act with the cyanide-metal compound baths therein to produce a result unexpected from an vexamination'of the attributes -of either my additionagents or the baths of the said patent, for

baths of such high concentration cannot be used to advantage without the metal compounds added by Westbrook.

lNhile I have discussed .above the use of baths of the Westbrook type, I do not wish to be limited in many respects, typical of lthose obtainable by the oxidation of amketaldoresins.

'I'he amaldacets are, of course, derived from certain "aliphatic ketaldones: the aldacets. Be-

20 low are discussed typical amketaldoresins derived from other aliphatic ketaldones and from carbocyclic ketaldones.

The following typical aliphatic ketaldones were tried as starting materials for the production 'of 25 amketaldoresins which could be oxidized accordcooo-aca'pipcorop ing to my invention.l The aldacets are'included for purposes of comparison. The compoundsv in the respective lists are given in about the order of their desirability as starting materials.

Aldehydes Aldol Acetaldehyde vCrotonaldehyde Paraldol y Propionaldehyde a-ethyl -propyl acrolein Butyraldehyde Acroleln Citral Citronellal Hexadecoic aldehyde Isobutylaldehyde Ketofnes Diethyl ketone Methyl n-propyl ketone Methyl ethyl ketone Diacetyl Light acetone oil Heavy acetone oil Isobutyl ketone .-Acetone Iso amyl ketone 'of amketaldoresins from the above aliphatic ketaldones, the following specific examples are given Example XV Equimolecular proportions of monoethanola-` Example XVI Methyl ethyl ketone was treated at roo-m tem- 70 perature with gaseous ammonia. The resulting reaction product, when oxidized, displayed activity as an addition agent in cyanide-cadmium plating baths.

Example XVII 75 AFive parts Vby weight of propionaldehyde was plating. The products thus considered above are,

in color.

Considering more specifically the preparation.

mixed with three parts by weight of sodium cyanide and ten parts by weight of water. The mixture was maintained at a temperature of about 50 C. for two hours and then allowed to cool. .There was a. change in the Aappearance of the mixture during the reaction period. The reaction product was a homogeneous, mobile liquid, light yellow in color.

The addition agent of this example was oxidized and used in a cyanide-cadmium bath such as that of Example XII, bath (l), the addition agent of this example being' used at a concentration of about 1.4 cc. per liter in lieu of the concentrated addition agent of Example XII. A bright. lustrous cadmium deposit was obtained, and the bath was characterized by good throwing power and a relatively wide bright current den-v sity range. Example XVIII Diethyl ketone was treated with sodium cyanide according to the procedure of Example XVII, and the reaction product permitted to stand a few days. The reaction mixture separated into two layers: a colorless lower layer, which is probably sodium .cyanide so1ution,' and an upper -layer light yellow in color. While I may use both layers mixed together, I prefer to separate, and use, the Y upper layer.

The yellow upper layer was oxidized with hydrogen peroxide and used in a cyanide-cadmium bath of the type shown in Example XII, bath (l) at an optimum concentration of 5 cc. per liter. Excellent results were obtained. The colorless lower layer, Veven when oxidized, displayed no appreciable activity as an addition agent.

Example XIX Methyl ethyl ketone was treated with sodium cyanide according to the procedure of Example XVII and then. allowed to stand a few days.v The reaction mixture separated into a lower, light yellow layer, and a small upper layer, dark red Again I may use the mixture, but I prefer to use the upper layer.

The upper, dark red layer was oxidized with peroxide and used at a concentration of G cc. per

` liter in acyanide-cadmium bath, of the type shown in Example XII, bath (1),-with fair resuits. The lower, light yellow layer, when oxidized, was not substantially effective as an addition agent in cyanide-cadmium plating.

Example XX Diacetyl was treated with sodium cyanide according to the `procedure of Example XVII, and a homogeneous liquid was obtained.

The diacetyl-cyanide 'reaction'product was oxidized and then employed at a concentration of 2 gcc. per' liter in a bath of the type shown in Example XII, bathI (1), with good results.

Example XXI j Methyl n-propyl ketone was treated with sodium cyanide according to the procedure of Example XIX. A colorless upper layer and a. colorless lower layer were obtained. Again I may use the reaction mixture, but I prefer to use the upper layer.

The upper layer was oxidized and was found to' be a good addition agent when employed at a concentration of 6 cc. per liter in a cyanide cadmium bath of the type shown in Example XII, bath 1). The lower layer, even when oxidized, showed no substantial elect'as an addition agent in cyanide-cadmium baths.

rmmplexxn v Acetone was treated with. sodium cyanide according to the procedure of Example XIX. After,

Example XXIII Butyraldehyde was treated with sodium cyanide according to1 the procedure of Example XIX. The two layers which formed may both be oxidized to use either or the mixture. 4

The lower layer, after oxidation, gave good results as an addition agent at a concentration of 15 cc. per liter in aA cyanide-cadmium 'bath of the type-shown in Example XII, bath (1). The upper layer, after oxidation, produced even better results at a concentration of only'5cc. per liter in a cyanide-cadmium bath/of the same type.

rample XXIV Hexadecoic aldehyde was treated with sodium cyanide according to the procedure lof Example X XVII, the mixture of aldehyde and cyanide being maintained at about 50 C. for four hours. ,The n reaction' mixture was allowed to stand overnight and was found to have separated with a top layer of nearly black. cyanide reaction product. lIt is noted that the original aldehyde was light yellow, Y 4o in` color. 4

y 'I'he lower layer, even when oxidized, had no appreciable eiIect as an addition agent in a cyanide-cadmium bath of the type shown in Example XII, bath (l). 'Ihel upper layer, after ,45 oxidation, was rather diiilcultly soluble, but at its optimum concentrationof 5 cc. per liter, it served asan addition agent in a; cyanide-cadmium bath of the same type. The top layer being poorly` soluble, it should be dispersed in the bath after the manner hereinbefore suggested. When aliphatic ketaldones are usedy as starting materials, a ketaldoneshould be selected which contains at least two 4 carbon atoms; Formaldehyde, with but one carbon atom, stands in a unique position with respect t0 alumnas` generally. Its dissimilarity to theother aldehydes is, of course, generally recognized.

Two hundred cubic centimeters of a forty'per o lcent-solution of formaldehyde was slowly added to a sdlution of sixty grams of sodium cyanide vin eighty cubic centimeters of water. The temperature rose rapidly, andthe reaction vesselL was cooled to maintain a temperature of about 45 to 65.50" c. After about two-thirds of the romane-- hyde was added, the addition of the remaining one-third producedno appreciable eil'ect.y After about ten minutes, however, the reaction mixture became hot and it was lnecessary to cool it. After the reaction was complete, a dark colored product ,was obtained. This product was tried as an addion agent, using from one to ten grams per liter `in a bath of the type shown in Example XII, bath (1) and it was found that the product had only a slight effect on the character of cadmium produce addition agents, and I mayA deposit. yNo substantial improvement resulted from oxidation of the agent. Y In view of the difference between formaldehyde and other aldehydes, one would expect formaldehyde to behave diil'erently as a starting -ma terial for the production of 'addition agents. Asv addition agents prepared from formaldehyde are of a different order of Aeffectiveness and are of a different character from the agents prepared from other aldehydes, I'prefer to employ ketaldones which have more than one carbon atom.

` As the aliphatic ketaldones contain more and more carbon atoms. they appear tofbecome less desirable as starting materials for the production of amketaldoresins. Citraleand citronellal, for example, with nine carbon atoms are quite satisfactory Aas starting materials for the production of addition agents, but the agents tend to be somewhat insoluble. They may, of course, be dispersed in the bath, but it is ordinarily preferable that the agents be readily solublein` the A amounts required.

Above about nine carbon atoms the aliphatic ketaldones become Y somewhat less desirable as ,starting materials. 'Hexadecoic aldehyde, for instance, with sixteen carbon atoms led to the production of a relatively insoluble, though operative; amketaldoresin. I prefer, accordingly, to employ aliphatic ketaldones containing between two and nine carbon atoms. This terminology includes acetaldehyde, for example, as a two carbon atom compound and citral as a nine carbon atom compound. I\especially prefer to employ those aliphatic' ketaldones' of two to nine, carbon atoms which contain no more than two hydroxyl groups. V Y Y I have found that it is not desirable that th aliphatic ketaldonesv contain ca rlmxylV groups. Moreover, the elements sulfur .and nitrogen are preferably absent from the aliphatic ketaldones l which I employ as starting materials for the production of-amketaldoresins. I-especially prefer ,to use aliphatic ketaldoneswhich 'contain only carbon, hydrogen, and oxygen, and in which the hydrogen-oxygen ratio is higher than that of Water.

While, as is'above noted, Iprefer that the aliphatic ketaldones which I employ asV starting materialls contain no more-than two hydroxyl groups; and, more specifically, that they have ahighe'r ratio of hydrogen to oxygen than that of water;

it is, nevertheless, within the scope of my present invention. to use such ketaldones as ketoses and aldoses. Y 5 e When carbohydrates which contain an aldehyde hr ketone group are treated with an amo or with analkali metal cyanide and then oxidized.

' products similar to those above may, with some diihculty, be prepared. The oxidized amketaldo-f resins thus produced, however, are of a different order of eifectiveness than the preferred, oxidized amketaldoresins.

The following example illustrates the production of an oxidized amketaldoresin from acarbohydrate which contains a ketaldonyl group.

Glucose was treated with an alkali metal cyanide by adding 12.3 grams of glucose to a cyanide solution made by adding 3.3v grams of' sodium' cyanide to l0 cubic centimeters of water.. The

At the endof the eighteen hours, the product was a dark red-brown, viscous liquid. This product was allowed to stand for about flve hours, and then four and one-half cubic centimeters of dilute sulfuric acid was added thereto. This quantity of sulfuric acid was an excess over the amount required to react with the unreacted sodium cyanide. A

When the acid was added, some heat was 10 evolved, and there was foaming of the product..

After the foam subsided, the-product was a clear,

red-brown, homogeneous liquid.

The product produced was oxidized with hydrogen peroxide and employed as an addition agent inv cyanide-cadmium baths of the ltype shown in Example XII in various concentrations up to ten grams per liter. The addition agent effected a considerable change in the character of the cadmium deposits, but was none too satisfactory. It is noted that the baths containing the addition agent were reddish-yellow in color. For purposes of direct comparison, glucose was employed as an addition agent for cyanide-cadmium baths of the same type and in the same concentrations as were the products of this example. Glucose itself Was much less eiective than its oxidized, cyanide-reaction product. It is noted that the baths containing glucose were light-yellow in color. A

The oxidized amketaldoresins prepared from the aliphatic ketaldones have been discussed above in detail, and itis now proposed to discuss briefly the preparation of oxidized amketaldoresins from carbocyclic ketaldones. Y

The' oxidized amketaldoresins may be prepared by the treatment of carbocyclic ketaldones with an amo or cyanide according to procedures similar to those above discussed.

The following carbocyclic ketaldones,v tried as starting -materials for the production of amketaldoresins, are listed inthe approximate order of their desirability.

. Cyclohexanone Methyl cyclohexanone Benzoin Benzaldehyde Anisic aldehyde Cinnamic aldehyde Quinone Vanillin Ortho-ortho dicarboxy benzoin In order more fully to describe the production of the oxidized amketaldoresins from the carbo- 55 cyclic ketaldones, the following illustrative examples are given:

Example XXVI Equimolecular proportions of monocthanol- 60 amine and benzaldehyde were reacted to room temperature, and then the reaction mixture was oxidized. The product displayed activity as an addition agentin a cyanide-cadmium plating bath of the type shown in Example XII, bath (l) 65 Eample XXVII Gaseous ammonia was passed into benzaldehyde until the reaction was complete. The amketaldoresin produced, after oxidation, was found 70 to have activity as an addition agent in a cyanidecadmium bath of the type shown in Example XII, bath (1).

Eample XXVIII Benzaldehyde was treated at 50 C. for several 75 hours with an excess of sodium cyanide solution.

Accordingly, I believe that the precipitate noted above was benzoin, and that on furthe'r treatment at 50 C. some further change took place which resulted in the formation of a more soluble compound. The benzoin may have reacted with ammonia, or cyanide, condensed further, or perhaps all.

' Etramgale` XXIX lBenzoin was treated as in Example XXVIII, l

and, after some time, the product was oxidized and a satisfactory addition agent was obtained. By dissolving the benzoin in alcohol and then treating the alcohol solution with cyanide, the nal product was made more quickly. In the latter procedure the alcohol was removed from the reaction product by distillation. The products obtained by treating' benzoin with cyanide, and oxidizing, were quite satisfactory addition agents in cyanide-cadmium baths of the type shown in Example XII, bath (l).

Example XXX Asothe starting materials, benzaldehyde and benzoin, are diicultly soluble, I added two carboxyl groups to benzoin thus:

COOH COOH H l C--C This ortho-ortho dicarboxy benzoin was much more soluble than benzoin, but it `was nonetoo satisfactory as a starting material for the production of addition agents. Ortho-orthodicarboxy benzoin was treated with cyanide, as in the'above examples, and, after oxidation, the productzwas found to possess some activity as an addition. agent in cyanide-cadmium baths.

The otler carbocycli'c compounds above listed may similarly be treated with an amo or cyanide according to the above procedures with good results. It is noted that instead of using methyl cyclohexanone, I may use other alkyl lsubstituted cyclohexanones.

oxygen and in which the hydrogen-oxygen ratio is greater than that'of water.

The foregoing discussion of the aromatic ketaldones is limited to a preferred group, the carbocyclic ketaldones. It will be understood, howT ever, that my invention in its broad aspects mcludes the use of cyclic ketaldones lgenerally. I may, for instance, use heterocyclie ke'taldones as starting materials for the preparation of addi- 10 Vtion agents for cyanide-cadmium plating baths.

The following example illustrates the practice of my invention usinga. heterocyclic ketaldone:

Example XXXI Six and one-half grams of freshly distilled furiural was added to a Sodium c'yanide solution made up of 3.3 grams of sodium cyanide in 10 cubic centimeters of water. Quickly there Wasproduced a red, heterogeneous mixture which Was then maintained for six hours at 45 to 50 C. During the reaction period, a faint odor of ammonia was observed. At the end of the six hours, the mixture had reacted toform a black, tarry, lower layer and a brown, supernatant liquid. lThe black lower layer, after oxidation, is

effective as an addition agent.

The reaction mixture-obtained above, before oxidation, was treated with an excess of dilute sulfuric acid over that required to react with excess-sodium cyanide, after the procedure of Example X. Upon the addition of acid, a violent reaction took place, and a small amunt of a black, liquid tar separated from the upper layer and joined the. tar already at the bottom of the 35 reaction receptacle.

The mixture of tars was employed, after oxidation, asanaddition agent in cyanide-cadmium baths of the type shown in Example`XII. The bathswere of a reddish color. Excellent results 40 were obtained, but theagent of this example did not cause the baths to display as extended a bright currentvdensity range as did the agents of Example X.

The agents of this example are rather dimcultly soluble, and it is preferred to add them to cyanide-cadmium; baths ,in a suitable solvent` such as alcohol. An optimum effect appears to be obtained when from, about one-half to twoy should be'noted in this connection that a great excess of cyanide is not satisfactory as, in effect,

the furfural would be present in too small a concentration for the proper reactions to take place. Furfural was employed as anl addition agent for cyanide-cadmium baths, of the type used iny Example XII, in various'amounts up to about ten grams per liter. After standing for several hours, the baths became very dark in color, and appeared black. vBy strong transmitted light, a

small sample of one such bath appeared to have a dark, wine color. While furfural, in relatively large amounts, displayed some activity as an addition agent, it was very much less eective than the oxidized, furfural-cyanide products of this example.

It will be understood therefore that in the production of amketaldoresins no such great departure from equimolecular 'proportions should be made. Itwill also be evident that thereacting materials should not be too dilute.

' In order conveniently to merchandise my novel addition agents, I may incorporate them with the dry ingredients employedto make up a plating bath. The resulting dry mixture can then be packaged and sold to the consumer who needs only to dissolve the mixture in water for use. Again, I may find itdesirable to incorporate the addition agent with only one or a few of the ingredients and let the consumer add the other ingredients. Frequently, of course, it will be desirable to merchandise the novel addition agents as such.

While I have disclosed a number of specific cyanide-cadmium baths heretofore, it will be understood that I do not intend to be limited thereby and that the teachings of my invention may be applied to cyanide-cadmium baths generally.

It will be also understood that I do not intend to be limited to the specific oxidized amketaldoresins above disclosed, as numerous other such compositions can readily be prepared by those skilled in the art according tothe principles of my invention.

I claim:

1. A cyanide-cadmium plating composition containing an oxidized amketaldoresin, the extent of oxidation of the amketaldoresin being less than that which would break up its carbon skeletons, an amketaldoresin being, as herein set forth, a pre-reacted compound prepared by reacting a ketaldone with an amo in alkaline solution.

2. A cyanide-cadmium plating composition containing an oxidized amketaldoresin derived from a carbocyclicketaldone, the extent of oxidation of the amketaldoresin being less than that which v.would break up its carbon skeletons, an amketaldoresin being, as hereinset forth, a pre-reacted compound prepared by reacting a ketaldone with an amo in alkaline solution.

3. A cyanide-cadmium plating composition containing an oxidized amketaldoresin derived from an aliphaticketaldone, the extent of oxidation of the amketaldoresin being less than that which would break up its carbon skeletons, an amketaldoresin being, as herein set forth, a pre-reacted compound prepared by reacting a ketaldone with an amo in alkaline solution.

4. A cyanide-cadmiumplating composition containing an oxidized amketaldoresin derived from an aliphatic ketaldone which contains only carbon, hydrogen, and oxygen, whichv has no less than two and no more than nine carbon atoms, and in which the ratio of hydrogen to oxygen is greater than that of water, the extent of oxidation of `the amketaldoresin being less than that which would break up its carbon skeletons, an amketaldoresinbeing, as herein set forth, a prereacted compound prepared by reacting a ketaldone with an amo in alkaline solution.

5. A cyanide-cadmium plating composition containing an oxidized reaction product of an alkali metal cyanide with a ketaldone, the extent of oxidation being less than that which would break up the carbon skeletons of thereaction products. 6. A cyanide-cadmium plating composition containing an oxidized reaction product of an alkali metal cyanide with a carbocyclic ketaldone, the extent of oxidation being less than that which would break up the carbon skeletons of the reaction products.

7. A cyanide-cadmium plating composition containing an oxidized reaction product of an alkali metal cyanide with an aliphatic ketaldone, the extent of voxidation being less than that which would break up the carbon skeletons of the reaction products.

8. A cyanide-'cadmium plating composition containing an oxidized reaction product of an alkali metal cyanide with an aliphatic ketaldone which contains only carbon, hydrogen, and oxygen, which has no less than two and no more than nine carbon Iatoms, and in which the ratio of hydrogen to oxygen is greater than that of Water, l the extent of oxidation being less than that which would break up the carbon skeletons of the reaction products.

9. A cyanide-cadmium plating composition containing an oxidized reaction product of an l alkali metal cyanide with an aldacet, the extent of oxidation being less than that which would break up the carbon skeletons of the reaction product, an aldacet being, as herein set forth, one

of the aldehyde equilibrium products which result when acetaldehyde is put in alkali metal cyanide solution.

10. A cyanide-cadmium plating composition containing an oxidized reaction product of an alkali metal cyanide with an aliphatic aldehyde selected from the group consisting of aldol, acetaldehyde, crotonaldehyde, and paraldol, the extent of oxidation being less than that which would break up the carbon skeletons of the reaction products.

11. A cyanide-cadmium plating composition containing an oxidized reaction product of an alkali metal cyanide with aldol, the extent of oxidation being less than that which would break up the carbon skeletons of the reaction products. 35 12. A cyanide-cadmiuml plating composition containing an oxidized amketaldoresin and a small amount of a metal of the iron group having an atomic yweight greater than yfifty-eight, the extent o oxidation of ie amketaldoresin being less than that which would break up its carbon skeletons, an amketaldoresin being, as herein set forth, a pre-reacted compound prepared by reacting a ketaldone with an amo in alkaline solution.

prepared ,by reacting a ketaldone with an amo in alkaline solution.

14. In a process for the electrodeposition of cadmium, the step comprising depositing cadmium from a cyanide-cadmium bath in the presence of an addition agent comprising an odxidized reaction product of an alkali` metal cyanide with a ketaldone, the extent of oxidation being less than that which would break up the carbon skeletons of the reaction products.

15. In a process for the electrodeposition of cadmium, the step comprising depositing cad mium from a cyanide-cadmium bath in the presence of an addition agent comprising an oxidized reaction product of an alkali metal cyanide of an aliphatic aldehyde selected from the group containing an oxidized reaction product of an.

amo with aldol, the extent of oxidation being less than that which would break up the carbon skeletons of the reaction product.

RICHARD O. 

